The present disclosure relates to a position measuring system and to a linear guide.
There are numerous applications known from practice in which it may be desirable to determine an absolute position for a first component that moves relative to a second component. Examples of such an application may be linear systems and linear guides, in particular, which can be used for various applications in handling engineering, particularly in linear engineering. To that end, there are numerous linear engineering opportunities for use as a machine component in machine construction, particularly in production or automation engineering.
By way of example, DE 10 2007 042 796 A1 reveals a linear guide with a guide carriage that can be moved along said linear guide. The linear guide described therein has an absolute material measure for determining an absolute position for the guide carriage in relation to the linear guide or to the material measure fitted thereto.
U.S. Pat. No. 4,009,377 A describes a method that allows determination of an absolute position for a guide carriage along a linear guide. To that end, for each distinguishable absolute position of the guide carriage, a respective pseudo random binary signal sequence (PRBS), which is also known and familiar by the term pseudo random binary sequence (PRBS), is produced by means of a shift register and put onto a material measure arranged along the linear guide. A sensor that can move relative to the material measure can scan a plurality of bits of the pseudo random binary signal sequence (PRBS) that are arranged next to each other. In order to determine the absolute position of the sensor and hence the absolute position of the guide carriage along the material measure, a shift register is filled with a bit sequence that corresponds to a zero position for the material measure. Next, the shift register is advanced as often as it takes for its content to match the measured value from the sensor. The recorded number of advances is a measure of the absolute position relative to the material measure.
A drawback of this is that numerous disturbing influences can result in an error in the scanning of the material measure or in the determination of the correct absolute position. This can cause corruption of the scan result or erroneous absolute position finding. Examples of these disturbing influences that cause errors are noise or unwanted electrical or electromagnetic effects, which can cause a bit error. As a result of this erroneous scanning or erroneous position finding, a workpiece can be rejected, for example, if production tolerances are exceeded on account of the erroneous position finding and resultant incorrect control of the guide carriage. Particularly also in safety-critical applications for a linear guide, it is desirable to achieve a high level of reliability for the absolute position finding for a guide carriage along a linear guide.
The object of the disclosure is therefore to provide a position measuring system that allows reliable absolute position finding.
This object is achieved by a position measuring system and a linear guide as described herein. Advantageous developments of the disclosure are specified in the subclaims.